Expansible drill bits for enlarging well bores



June 1955 A. w. KAMMERER, JR 2,710,172

EXPANSIBLE DRILL BITS OR ENLARGING WELL BORES 2 Sheds-Sheet 1 jg I.

I c I 3.

Filed Nov. 25. 1953' IN V EN TOR.-

4420/52 7V: KAMMEPEE, (IQ.

A TTQEA/EY- June 7, 1955 w. KAMMERER, JR 2,710,172

EXPANSIBLE DRILL BITS FOR ENLARGING WELL BORES Filed Nov. 25, 1953 2Sheets-Sheet 2 INVENTOR. APCHEE KAMMEEEE, :19.

BY I

4 T TOQNEY- United States Patent EXPANSIBLE DRILL BITS FOR ENLARGINGWELL BORES Archer W. Kammerer, Jr., Fullerton, Califi, assignor, by

direct and mesne assignments, to Rotary Oil Tool Company, HuntingtonPark, Califi, a corporation of California Application November 23, 1953,Serial No. 393,772

18 Claims. (Cl. 255-76) The present invention relates to rotary drillbits of the expansible type for drilling or enlarging well bores belowwell casing to a larger diameter than the inside diameter of the wellcasing itself.

Expansible drill bits are known in which the cutters are expandedlaterally outward and locked in such expanded position through themedium of a mandrel telescopically arranged in the body of the drillbit. It is necessary to move the mandrel down relative to the body tolock the cutters in an outward position. Elevation of the mandrel withrespect to the body releases the cutters from their locked condition,enabling them to move inwardly toward retracted position. 7

Certain disadvantages are associated with bits of th above type, in thata downward force must be maintained on the mandrel to hold it in itslocked position, for the purpose of securing the cutters in theirexpanded position. Elimination of this downward force, which may occuras a result of the cutters no longer engaging a formation shoulder,permits the body and cutters to move or drop down with respect to themandrel, thereby, in effect, producing relative elevation of the mandrelwithin the body and shifting of the mandrel to an unlocked position thatcould allow the cutters to retract, at least partially. It then becomesnecessary to reshift the mandrel downwardly of the body, to again lockthe cutters in their fully expanded position.

It is an object of the present invention to provide an expansible typeof rotary drill bit in which the cutters are locked automatically intheir fully expanded position Without the necessity for moving amandrel, telescopically arranged in the bit body, downwardly of thebody. The locking action occurs as a result of structure embodiedin thebit itself, and without the need for-imposing any external forces on thebit.

Another object of the invention is to provide an expans ible rotarydrill bit of the type having a mandrel connectible to a drill stringtelescopically arranged in the bit body, in which the cutters are lockedautomatically in their maximum outwardly expanded position without thenecessity for imposing drilling weight on the cutter'spor for moving themandrel with respect to the body.

A further object of the invention is to provide an expansiole rotarydrill bit in which the cutters can be locked in their outwardly expandedposition by a combination of spring force, hydraulic force and drillingweight imposed 1 on the cutters, or by one or more of theforegoing.

Another object of the invention is to provide an expansible rotary drillbit, in which the cutters are locked automatically in their fullyexpanded position without the necessity for telescoping the mandrel withrespect tocompanying and forming part of the present specification. Itwill now be described in detail, for the purpose of illustrating thegeneral principles of the invention; but it is to be understood thatsuch detailed description is not to be taken in a limiting sense, sincethe scope of the invention is best defined by the appended claims.

Referring to the drawings:

. Figure l is a longitudinal section through an embodiment of theinvention disposed in a well bore, with the cutters and other parts intheir initial retracted position;

Fig. 2 is a longitudinal section, similar to'Fig. 1, disclosing thecutters locked in their fully expanded position prior to the impositionof drilling weight on the cutters;

Fig. 3 is a longitudinal section, similar to Fig. 1,disclosing thecutters locked in their outwardly expanded position and with downward ordrilling weightbeing imposed on the cutters;

Fig. 4 is a longitudinal section, similar to Fig. 1, disclosing thelocking portion of the device shifted to a retracted position to enablethe cutter mechanism to be returned to its retracted position Within awell casing.

The expansible drill bit A disclosed in the drawings is of the generaltype shown in the patent to Archer W. Kammerer, Patent No. 2,545,036, towhich attention is invited. The rotary drill bit is attached to a stringof drill pipe 13, by means of which it is lowered through a well casingC in a well bore D to a point below the casing shoe E at which thediameter of the bore hole is to be enlarged. The drill bit may have apilot bit 10 at its lower end for centering the tool in a hole that mayhave already been drilled, or for drilling the central portion pander 23beats.

of a compressed coil spring, is received within a retainer. pocket 24 inthe body and exerts its force against the of a new hole, in the absenceof a pre-existing hole. The main portion of the bit is capable ofenlarging the bore hole by producing and operating upon a formationshoulder F, as hereinafter described.

The main body 11 of the bit has a plurality of expansible parts mountedon it, comprising cutter supporting members 12 pivotally mounted in bodyslots 13 on hinge pins 14 suitably welded to the body. Each cuttersupporting member consists of a depending leg 15 having a bearingsupporting pin 16 inclined inwardly and down-' wardly and on which aroller side cutter 17 is rotatably mounted. Anti-friction roller andball bearing elements 18, 19 are preferably placed between each cutterand bearing pin, the roller bearings 18 transmitting radial thrusts andthe ball bearings 19 both radial and axial thrusts. The ball bearingsalso retain each cutter on a pin 16, being inserted in place through apassage 20 in the bearing support, which is then closed by a plug 21welded to the pin. The plug 21 depends from the passage andis used tohold the cutters 17 in retracted position, as explained below.

Each cutter supporting member 12 also includes an upwardly extending arm22 against which an elastic ex- This expander, which 'is in the form arm21, tending to swing the latter inwardly and thus urge the cutter 17 on'the'other side of the fulcrum pin 14 in an outward direction. Theextent of this outward movement is limited by engagement of a suitablestop shoulder 25' on each cutter supporting member 12 with acooperablestop portion 26 on the body 11. 7

After the cutters 17 have been expanded outwardly by the springs 23 to amaximum extent, they can be locked in this position by a tubular member27 of a composite lar member 27 is provided with a lock portion 31 atits lower region movable from an upper position in transverse alignmentwith inner supporting member recesses 32, which allow retraction of thecutters 17, to a lower position opposite lugs 33 formed on andprojecting inwardly from the cutter supporting legs 15, which preventsretraction of the cutters.

As stated above, the tubular member 27 is telescopically arranged withinthe Kelly portion of the mandrel, the member 27 and Kelly 30 beingcapable of partaking of relative longitudinal movement. The upperportion 30a of the Kelly has an upper threaded pin 34 connected to acollar 35 threadedly secured to the lower end of the string of drillpipe B extending to the top of the well bore.

A lower Kelly member 30b is threadedly attached to the upper Kellymember 30a, being disposed within the upper portion of the body 11 andslidably splined to the latter. Such slidable splining is secured bymaking the ex terior 36 of the Kelly of non-circular or hexagonal shape,which is telescopically received in a companion non-circular orhexagonal socket 37 formed in the body. The Kelly 30 has a limited rangeof movement within the body. Its upward movement is restrained by theengagement of an external shoulder 38 on the lower Kelly portion 30b,disposed within a counterbore 39 in the body, with the lower end of ayieldable stop and body supporting spring 40, the upper end of whichengages a retainer ring 41 at the upper end of the body 11 which may besecured to the latter, as by the use of welding material 42.

The body supporting spring causes the Kelly 30 to yieldably support thebit body 11 and the cutter mechanism carried thereby in an intermediateposition with respect to the Kelly. However, the Kelly 30 is stillmovable upwardly, as explained hereinbelow, with respect to the body,such relative upward movement being permitted by the compression of thespring 40. The Kelly is also capable of movement downwardly of the bodyto a limited extent, determined by the engagement of the lower end 43 ofthe lower Kelly portion 30b with the connecting flange 44 of a springhousing 45 which rests upon a body shoulder 46. This spring housing 45is secured to the body by one or more screws 47 threaded transverselythrough the body and disposed within a pcripheral groove 48 in theconnecting flange 44.

In the specific tool disclosed in the drawings, the tubular member 27cannot move downwardly to dispose its lock .ring 31 behind thesupporting member lugs 33 until the supporting members 12 and theircutters 17 have been expanded outwardly to their maximum extent. Themember 27 is prevented from moving downwardly until this conditionoccurs by virtue of the fact that the lower end of the lock ring 31rests upon the upper portions of the lugs 33 (.Fig. 1). After the cuttersupporting members and cutters have been expanded outwardly to theirmaximum extent, the lock ring 31 of the tubular member is automaticallyshifted downwardly, to be disposed behind the lugs 33 independently ofthe movement of the Kelly 30. A spring force is availed of foraccomplishing this purpose. Thus, the spring housing 45 extends upwardlyaround the tubular mandrel member 27 and has a thrust head or upperspring seat 49 extending inwardly toward the tubular member. A helicalcompression spring 59 encompasses the member 27, its upper nd engagingthe upper thrust head 49 and its lower end alower mandrel head or springseat 51, so that the compression spring 50 tends to move the tubularmember 27 in a downward direction. Such downward movement can occurafter the cutters 17 have been expanded outwardly to the maximumposition, inasmuch as an upperhead '52 on the tubular member is spacedinitially a sufficient distance above the upper end of the springhousing head 49 and the tubular member head 52 is also disposed asuflicient distance above an inwardly extending release shoulder 53 iii)formed on the lower Kelly portion 30!). After the cutter supportingmembers 12 and cutters 17 have been expanded outwardly to the maximumextent, the spring 50 can expand, to shift the tubular member 27downwardly and dispose the lock ring 51 in its locking position behindthe supporting member lugs 33. This position is definitely located bythe engagement of the lower surface 54 of the tubular member head 52with the upper end of the spring housing 45, as disclosed in Fig. 2.

If desired, the tubular member head 52 may be constituted as a pistonslidable along an inner cylindrical wall 55 of the lower Kelly member30b. Leakage of fluid between the piston and cylindrical wall in adownward direction may be prevented by providing a suitable piston ring56, such as a rubber O ring, in a ring groove 56 in the piston whichslidably and sealingly engages the cylindrical wall 55. If need be ordesired, the mandrel member 27 may be moved downwardly hydraulically bythe application of hydraulic pressure to the upper surface of the piston52, urging it and its tubular member 27 downwardly, to dispose the lockportion or ring 31 behind the supporting member lugs 33.

The compression spring Si) is constantly urging the tubu lar member 27in a downward direction toward its locking position behind the lugs.However, such downward movement is initially prevented by holding thecutters 17 and their supporting members 12 positively in an inwarddirection, so that the lower end of the lock portion 31 rests upon upperportions of the lugs 33. As disclosed in the drawings, a hydraulicallyreleasable latch or holding device is employed. This holding deviceincludes a holding member 57 secured to the lower end oi a central rod58 whose upper end projects into a passage 59 extending completelythrough the tubular member 27. This passage communicates with a centralpassage 60 extending upwardly through the Kelly portion 30 of thetubular mandrel 28. The passage 59 through the tubular member 27 issubstantially smaller in diameter than the passage 60 through the Kelly.A head 61 is secured to the upper end of the rod 58, having substantialclearance in the passage 59 to allow fluid to pass upwardly into thecentral passages 59, 6t) and into the drill string B. The holding member57 has spaced holes 62 in its outer portion for receiving the lower endsof the bearing plugs 21.

When the holding device 57 is disposed over the plugs 21, the cuttersupporting members 12 are prevented from expanding under the influenceof the springs 23, thereby holding the cutters 17 in retracted position.Such retr-acted condition of the cutter supporting members 12 preventsthe helical compression spring 50 from shifting the tubular member 27downwardly to its locking position. The holding member 57 can bereleased from the plugs 21 as a result of fluid pressure actingdownwardly F on a ball 63, which can be disposed in the passage 59 andwhich will come to rest on the head 61, the ball having substantiallythe .same diameter as the diameter of thepassage 59, to allow fluidpressure to be built up thereabove. When fluid pressure is applied tothe fluid in the drill pipe B and the mandrel passages 60, 59, it canshift the ball 63, rod 58 and holding member 57 downwardly, to free thelatter from the plugs 21 and allow the .springs .23 to move the arms 21inwardly and the cutters 17 outwardly. The drill pipe B and drill bit Aare rotated, the springs 23 urging the cutters 17 outwardly until theyare in their fully expanded position and have produced a formationshoulder F in the wall of the well bore D. Thereafter, the compressionspring 50 is effective to shift the tubular member 27 downwardlyautomatically, to place its lock portion 31 behind the sup 5i portingmember lugs 33, to positively hold the cutters in the drill pipe Bdownwardly, which shifts the Kelly portion of the mandrel in a downwarddirection to the extent determined by engagement of its lower end 43 onwith the connecting flange 44 of the spring housing 45. When suchengagement occurs, the lower end 64 of the upper Kelly section 30a ispreferably disposed contiguous the upper end of the tubular member heador piston 52, which provides a positive stop limiting upward movement ofthe tubular member 27 with respect to the body 11 (Fig. 3).

In the operation of the drill bit in a well bore, the cutters 17 andtheir supporting members 12 are locked in their retracted position bythe hydraulically releasable latch device 57, the parts occupying theposition disclosed in Fig. l. The tubular member 27 is in its upwardposition, its lock portion 31 engaging the upper portions of thesupporting member lugs 33, with the tubular member head or piston 52disposed adjacent the lower end 64 of the upper Kelly section 33a andsubstantially above the upper end of the spring housing 45 and therelease shoulder 53 on the lower Kelly section 30b. The yieldable bodysupporting spring is holding the body of the tool and the other parts ina desired upper position with respect to the mandrel 28, so as toappropriately locate the parts in the position shown in Fig. l, with thelower end 43 of Kelly 30 an appropriate distance above the flange 44.

The apparatus is lowered through the casing C to the open well bore Dtherebelow, and, when the region in the latter is reached at which thehole enlarging operation is to occur, pressure is applied to the fluidin the drill pipe B, to move the ball 63 into the tubular member passage59 and into engagement with the rod head 61 of the latch mechanism. Theapplication of sufiicient pressure on this ball 63 moves it and thelatch 57 downwardly, to shift the latter oif the plugs 21 secured to thecutter supporting members 12. When such release occurs, the tubularstring B can be rotated, the springs 23 urging the arms 21 inwardly andforcing the cutters 17 outwardly into engagement with the wall of thewell bore D. Rotation of the drill pipe B rotates the Kelly portion 30of the mandrel 28, and, through the splined connection 36, 37, the body11 of the tool, the cutters 17 beginning to dig into the wall of thewell bore. During such rotation, no drilling weight is imposed on thetool, so that the mandrel portion 28 of the apparatus still occupiesessentially the position disclosed in Fig. 1. When the springs 23 haveexpanded the cutters 17 outwardly to their maximum extent, the mandrelcompression spring 50 is then effective to immediately shift the tubularmember 27 downwardly, to dispose its lock portion 31 behind the lugs 33,the tubular member head 52 engaging the upper end of the cylindricalhousing (Fig. 2).

Inasmuch as the drilling mud is usually being pumped down the drill pipeB and through the tool A at this time, for the purpose of removing thecuttings to the top of the well bore, a hydraulic force is alsoavailable, acting on the tubular member head or piston 52, to urge thelatter in a downward direction, in view of the throttling effect of thefluid as it enters the smaller diameter passage 59 through the tubularmember 27. Accordingly, should the spring 50, for some reason, beincapable of shifting the tubular member 27 downwardly to its fullestextent, then a hydraulic force is available to insure the shifting ofthe tubular member downwardly to its locked position. Accordingly, it isevident that the force of the compression spring 56 is supplemented by ahydraulic force acting on the piston 52, to insure the disposition ofthe lock portion 31 behind the lugs 33.

It is to be noted that the tubular member 27 has moved downwardly to itslocked position behind the cutter supporting members ,IZautomaticallyafter the.

latter have been expanded outwardly to their maximum extent. It isunnecessary for the operator to partake of any other action. After theformation shoulder F has been produced and it is desired to drill awaythe hole to the enlarged diameter, downweight is imposed on the drillpipe B, which will shift the Kelly portion 30 of the composite mandrel28 downwardly of the body 11 and of the spring housing 45, to the extentlimited by engagement of the lower end 43 of the Kelly 30 with thespring housing flange 44. The drilling weight is then transferreddirectly from the Kelly 30 to the body 11, and from the latter to thecutter supporting members 12 and cutters 17. This position of the partsis disclosed in Fig. 3, from which it will be noted that the lower end64 of the upper portion 30a of the Kelly has now been disposedimmediately above the tubular member head or piston 52, which willfurther insure the retention of the tubular member 27 in its downwardlocked position behind the cutter supporting members 12.

Drilling will proceed to the desired extent, with the cutters 17 lockedin their outward position. Should the apparatus be elevated, to raisethe cutters above the formation shoulder F, then the tubular member 27will still remain in its locked position, inasmuch as the spring iseffective to hold the mandrel member 27 in its downward postition, theforce of this spring being supplemented by the action of the fluidpressure acting on the upper surface of the piston 52, assuming that thepumping of the drilling fluid through the apparatus continues.Accordingly, it is evident that the parts remain in their outward lockedposition, regardless of the elevation or lowering of the drill string.Moreover, it is to be noted that it is unnecessary for the cutters 17 toremain in engagement with the formation shoulder F, or the like, and fordrilling weight to be imposed on the cutters, for the purpose of holdingthem locked in their outwardly expanded position.

When it is desired to retrieve the expansible drill bit A from the wellbore, the drilling fluid is no longer pumped through the tool and thedrill pipe B is elevated, the tool being moved up the hole until asmaller diameter portion or the casing shoe E is reached. When thisoccurs, the outer surfaces of the cutter supporting members 12 engagethe lower end of the shoe E and tend to prevent upward movement of thebit body 11. An upward strain can then be taken on the drill pipe B andon the kelly 30 of the tool, the releasing shoulder 53 on the lowerkelly portion 30b engaging the underside of the tubular member head orpiston 52, to forcibly pull the tubular member 27 in an upward directionagainst the action of the compression spring 50 surrounding the tubularmember. The tubular member 27 is thus pulled upwardly, to relocate itslocking portion 31 in alignment with the supporting member recesses 32and above the lugs 33, which then allows the casing shoe E to urge thecutter sup porting legs 15 and cutters 17 in an inward direction,disposing the lugs 33 under the lock portion 31 and thereby preventingthe compression spring 50 from re-- shifting the tubular member 27 in adownward direction into its lock-ed position behind the lugs- The upwardmovement of the kelly portion 30, for the purpose of forcibly moving thetubular member 27 upwardly to its released position is permitted, sincethe body supporting spring 46 will merely be compressed to a furtherextent. as the release shoulder 53 carries the tubular memberv head 52upwardly to its initial position above the upper end of the springhousing 45 (Fig. 4). After the cutter supporting members 12 have beenshifted inwardly by the casing shoe E, they are held inwardly by thewall of the well casing C, to secure the lugs 33 under the lock portion31 of the tubular mandrel member 27 When this occurs, it is immaterialwhether the kelly portion 30 of the tool is lowered with respect to thebody 11, since the compression spring 50 is then incapable of reshiftingthe tubular member 27 back to its locked position within and behind thesupporting member lugs 33.

The tool A may now be elevated in the well casing C and withdrawncompletely from the well bore.

It is, accordingly, apparent that an expansible rotary drill bit hasbeen provided in which the cutters 17 and their supporting members 12are positively locked in their outward position automatically,regardless of the downward movement of the Kelly portion 30 of themandrel with respect to the body 11 of the tool. The lock device 31 isshifted to and held in its locked position behind the cutter supportingmember lugs 33 by the force being exerted constantly by the compressionspring 5%. This force may be supplemented, if desired, by the pressureof the fluid being pumped through the apparatus and acting on the upperpiston 52. Of course, it is not necessary that the upper piston 52 beused at all. The upper member 52 may merely constitute a guide head forthe tubular member 27, to insure its proper longitudinal movement withrespect to the other parts. In addition to the presence of the springforce and the hydraulic force to hold the lock member 31 behind thesupporting member lugs 33, the imposition of downweight on the upparatus provides an additional mechanical holding device by locating theKelly portion 3% of the tool immediately above the tubular member head52, which further prevents the lock portion of the mandrel from beingretracted from its locking position behind the supporting member lugs.

In the event that the application of drilling weight to the cutters isdiscontinued, as through elevation of the Kelly portion 30 of themandrel within the body, the tubular member 27 will still remain in itslocked position behind the cutter supporting members 12, such result being produced by the compression spring 59 and by the hydraulic force ofthe drilling fiuid acting on the piston 52, if a piston is provided inthe apparatus. Regardless of such retention of the tubular mandrelmember 27 in its locked position, it is still capable of being forciblyreleased from such locked position upon elevation of the apparatus inthe well bore, and particularly into the casing string C.

The inventor claims:

1. A rotary well drilling bit, including a main body,

having'a connection for securing said mandrel member directly to a drillstring, said mandrel member being slidably splined to said body, asecond mandrel member telescopically related to said first mandrelmember and movable relatively downward of said body to hold said cuttermeans laterally outward, and means operatively $1.

engaging said body and second mandrel member to urge said second mandrelmember relatively downward of said body and first mandrel member.

2. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel member having aconnection for securing said mandrel member directly to a drill string,said mandrel member being slidably splined to said body, a secondmandrel member movable longitudinally with respect to said body andfirst mandrel member in one direction to hold said cutter meanslaterally outward, and means operatively engaging said body and secondmandrel member to urge said second mandrel member in said onelongitudinal direction relative to said body and first mandrel member.

3. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel memberconnec'tible to a drill string and slidably splined to said body, asecond mandrel. member movable longitudinally with respect to said bodyand first mandrel Lil member in one direction to hold said cutter meanslater ally outward, and means operatively engaging said body and secondmandrel member to urge said second mandrel member in said onelongitudinal direction relative to said body and first mandrel member,said first mandrel member being movable in said one longitudinaldirection with respect to said body into juxtaposed relation to saidsecond mandrel member to prevent longitudinal movement of said secondmandrel member in the opposite longitudinal direction.

4. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel memberconnectihle to a drill string and slidably splined to said body, asecond mandrel member telescopically related to said first mandrelmember and movable relatively downward cl said body to hold said cuttermeans laterally outward, and means operatively engaging said body andsecond mandrel member to urge said second mandrel member relativelydownward of said body and first mandrel member, said first mandrelmember being moved downwardly with respect to said body into juxtaposedrelation to said second mandrel member to prevent upward movement ofsaid second mandrel member out of its position holding said cutter meanslaterally outward.

5. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward cf said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel member having aconnection for securing said mandrel member directly to a drill string,said mandrel member being slidably splined to said body, a secondmandrel member movable longitudinally with respect to said body andfirst mandrel member in one direction to hold said cutter meanslaterally outward, means operatively engaging said body and secondmandrel member to urge said second mandrel member in said onelongitudinal direction relative to said body and first mandrel member,and means on said first mandrel member engageable with said secondmandrel member to shift said second mandrel member in the oppositelongitudinal direction out of holding relation to said cutter means.

6. A rotary well drilling bit, including a main body,

cutter means mounted on said body for expansion laterally outward ofsaid body, means for expanding and holding said cutter means laterallyoutward, said expanding and holding means comprising a first mandrelmember having a connection for securing said mandrel member directly toa drill string, said mandrel member being slidably splined to said body,a second mandrel member telescopically related to said first mandrelmember and movable relatively downward of said body to hold said cuttermeans laterally outward, means operatively engaging said body and secondmandrel member to urge said second mandrel member relatively downward ofsaid body and first mandrel member, and means on said first mandrelmember engageable with said second mandrel member to shift said secondmandrel member upwardly out of holding relation to said cutter means.

7. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel memberconnectible to a drill string and slidably splined to said body, asecond mandrel member movable longitudinally with respect to said bodyand first mandrel member in one direction to hold said cutter meanslaterally outward, means operatively engaging said body and secondmandrel member to urge said second mandrel member in said onelongitudinal direction relative to said body and first mandrel member,said first mandrel member being movable in said one longitudinaldirection with respect to said body into juxtaposed relation to saidsecond mandrel member to prevent longitudinal movement of said mandrelmember in the opposite longitudinal direction, and means on said firstmandrel member engageable with said second mandrel member to shift saidsecond mandrel member in the opposite longitudinal direction out ofholding relation to said cutter means.

8. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel memberconnectible to a drill string and slidably splined to said body, asecond mandrel member telescopically related to said first mandrelmember and movable relatively downward of said body to hold said cuttermeans laterally outward, means operatively engaging said body and secondmandrel member to urge said second mandrel member relatively downward ofsaid body and first mandrel member, said first mandrel member beingmoved downwardly with respect to said body into juxtaposed relation tosaid second mandrel member to prevent upward movement of said secondmandrel member out of its position holding said cutter means laterallyoutward, and means on said first mandrel member engageable with saidsecond mandrel member to shift said second mandrel member upwardly outof holding relation to said cutter means.

9. A rotary well drilling bit, including a main body, cutter meansmounted on said body, means engaging said cutter means for expandingsaid cutter means laterally outward of said body, a first mandrel memberhaving a connection for securing said mandrel member directly to a drillstring, said mandrel member being slidably splined to said body, asecond mandrel member movable relatively downward of said body to holdsaid cutter means laterally outward, and means operatively engaging saidbody and second'mandrel member to urge said second mandrel memberrelatively downward of said body and first mandrel member.

10. A rotary well drilling bit, including a main body, cutter meansmounted on said body, means engaging said cutter means for expandingsaid cutter means laterally outward of said body, a first mandrel memberconnectible to a drill string and slidably splined to said body, asecond mandrel member movable relatively downward of said body to holdsaid cutter means laterally outward, and means operatively engaging saidbody and second mandrel member to urge said second mandrel memberrelatively downward of said body and first mandrel member, said firstmandrel member being movable downwardly with respect to said body intojuxtaposed relation to said second mandrel member after said secondmandrel member has been shifted into holding relation to said cuttermeans to prevent upward movement of said second mandrel member out ofholding relation to said cutter means.

11. A rotary well drilling bit, including a main body, cutter meansmounted on said body, means engaging said cutter means for expandingsaid cutter means laterally outward of said body, a first mandrel memberconnectible to a drill string and slidably splined to said body, asecond mandrel member movable relatively downward of said body to holdsaid cutter means laterally outward, means operatively engaging saidbody and second mandrel member to urge said second mandrel memberrelatively downward of said body and first mandrel member, said firstmandrel member being movable downwardly with respect to said body intojuxtaposed relation to said second mandrel member after said secondmandrel member has been shifted into holding relation to said cuttermeans to prevent upward movement of said second mandrel member out ofholding relation to said cutter means, and means on said first mandrelmember engageable with said second mandrel member to shift said secondmandrel member upwardly out of holding relation to said cutter means.

12. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and hold ing said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel member having aconnection for securing said mandrel member directly to a drill string,said mandrel member being slidably splined to said body, a secondmandrel member telescopically related to said first mandrel member andmovable relatively downward of said body to hold said cutter meanslaterally outward, and spring means operatively engaging said body andsecond mandrel member to urge said second mandrel member relativelydownward of said body and first mandrel member.

13. A rotary Well drilling bit, including a main body,

downward of said body to hold said cutter means laterally outward,spring means operatively engaging said body and second mandrel member tourge said second mandrel member relatively downward of said body andfirst mandrelmember, and hydraulic means connected to said secondmandrel member to urge said second mandrel member relatively downward ofsaid body and first mandrel member in response to fluid pressure in thedrill string.

14. A rotary well drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel memberconnectible to a drill string and slidably splined to said body, asecond mandrel member telescopically related to said first mandrelmember and movable relatively downward of said body to hold said cuttermeans laterally outward, and spring means operatively engaging said bodyand second mandrel member to urge said second mandrel member relativelydownward of said body and first mandrel member, said first mandrelmember being movable downwardly with respect to said body intojuxtaposed relation to said second mandrel member to prevent upwardmovement of said second mandrel member out of holding relation to saidcutter means.

15. A rotary well. drilling bit, including a main body, cutter meansmounted on said body for expansion laterally outward of said body, meansfor expanding and holding said cutter means laterally outward, saidexpanding and holding means comprising a first mandrel memberconnectible to a drill string and slidably splined to said body, asecond mandrel member telescopically relative to said first mandrelmember and movable relatively downward of said body to hold said cuttermeans laterally outward, spring means operatively engaging said body andsecond mandrel member to urge said second mandrel member relativelydownward of said body and first mandrel member, said first mandrelmember being movable downwardly with respect to said body intojuxtaposed relation to said second mandrel member to prevent upwardmovement of said second mandrel member out of holding relation to saidcutter means, and means on said first mandrel member engageable withsaid second mandrel member to shift said second mandrel member upwardlyout of holding relation to said cutter means.

16. A rotary well drilling bit, including a main body, cutter meansmounted on said body, means engaging said cutter means for expandingsaid cutter means laterally outward of said body, a first mandrel memberhaving a connection for securing said mandrel member directly to a drillstring, said mandrel member being slidably splined to said body, asecond mandrel member movable relatively downward of said body to holdsaid cutter means laterally outward, and spring means operativelyengaging said body and second mandrel member to urge said second mandrelmember relatively downward of said body and first mandrel member.

17. A 'rotar well drillin bit, including a main body,

cutter means mounted on said body, means engaging said cutter means forexpanding said cutter means laterally outward of said body, a firstmandrel member connectible to a drill string and slidably splined tosaid body, a second mandrel member movable relatively downward or": saidbody to hold said cutter means laterally outward, spring meansoperatively engaging said body and second mandrel member to urge saidsecond mandrel member relatively downward of said body and first mandrelmember, said first mandrel member being movable downwardly with respectto said body into juxtaposed relation to said second mandrel memberafter said second mandrel member has been shifted into holding relationto said cutter means to prevent upward movement of said second mandrelmember out of holding relation to said cutter means, and means on saidfirst mandrel member engageable with said second mandrel member to shiftsaid second mandrel member upwardly out of bold ing relation to saidcutter means.

18. A rotary well drilling bit, including a main body, cutter meansmounted on said body, means engaging said cutter means for expandingsaid cutter means laterally outward. of said body, a first mandrelmember connectible to a drill string and slidably splined to said body,a second mandrel member movable relatively downward of said body to holdsaid cutter means laterally outward, spring means operatively engagingsaid body and second mandrel member to urge said second mandrel memberrelatively downward of said body and first mandrel member, said firstmandrel member being movable downwardly with respect to said body intojuxtaposed relation to said second mandrel member after said secondmandrel member has been shifted into holding relation to said cuttermeans to prevent upward movement of said second mandrel member out ofholding relation to said cutter means, means on said first mandrelmember engageable with said second mandrel member to shift said secondmandrel member upwardly out of holding relation to said cutter means,and hydraulic means connected to said second mandrel member andshiftable by fluid pressure in the drill string for urging said secondmandrel member relatively downward of said body and first mandrelmember.

References (Iitetr in the file of this patent UNZTED S ATES PATENTS473,909 Bullock May 3, 1892 1,708,932 Brown Apr. 16, 1929 FOREIGNPATENTS 21,696 Great Britain 1901

